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client-ip=165.204.84.17; helo=satlexmb08.amd.com; pr=C Received: from satlexmb08.amd.com (165.204.84.17) by SJ1PEPF00001CE5.mail.protection.outlook.com (10.167.242.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9456.9 via Frontend Transport; Wed, 24 Dec 2025 05:45:42 +0000 Received: from satlexmb08.amd.com (10.181.42.217) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Tue, 23 Dec 2025 23:45:41 -0600 Received: from [10.85.35.110] (10.180.168.240) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server id 15.2.2562.17 via Frontend Transport; Tue, 23 Dec 2025 23:45:36 -0600 Message-ID: <3e56e2f1-42bd-45e6-90a7-4105386d63ed@amd.com> Date: Wed, 24 Dec 2025 11:15:30 +0530 Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Patch v5 13/19] perf/x86: Enable SSP sampling using sample_regs_* fields To: Dapeng Mi CC: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Thomas Gleixner , Dave Hansen , Ian Rogers , Adrian Hunter , Jiri Olsa , Alexander Shishkin , Andi Kleen , Eranian Stephane , Mark Rutland , , , , Zide Chen , "Falcon Thomas" , Dapeng Mi , "Xudong Hao" , Kan Liang , "Ravi Bangoria" References: <20251203065500.2597594-1-dapeng1.mi@linux.intel.com> <20251203065500.2597594-14-dapeng1.mi@linux.intel.com> Content-Language: en-US From: Ravi Bangoria In-Reply-To: <20251203065500.2597594-14-dapeng1.mi@linux.intel.com> Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Dec 2025 05:45:42.0129 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 01fda748-1c67-4474-5837-08de42afacf2 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SJ1PEPF00001CE5.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH1PR12MB9575 Hi Dapeng, > This patch enables sampling of CET SSP register via the sample_regs_* > fields. > > To sample SSP, the sample_simd_regs_enabled field must be set. This > allows the spare space (reclaimed from the original XMM space) in the > sample_regs_* fields to be used for representing SSP. > > Similar with eGPRs sampling, the perf_reg_value() function needs to > check if the PERF_SAMPLE_REGS_ABI_SIMD flag is set first, and then > determine whether to output SSP or legacy XMM registers to userspace. 1. The userspace SSP is saved in REGS_INTR even though interrupt regs are of kernel context. Would it be better to pass 0 instead (see the _untested_ patch below). --- a/arch/x86/kernel/perf_regs.c +++ b/arch/x86/kernel/perf_regs.c @@ -71,7 +71,7 @@ u64 perf_reg_value(struct pt_regs *regs, int idx) return perf_regs->egpr_regs[idx - PERF_REG_X86_R16]; } if (idx == PERF_REG_X86_SSP) { - if (!perf_regs->cet) + if (!perf_regs->cet || !user_mode(regs)) return 0; return perf_regs->cet->user_ssp; } 2. Could a simple "--user-regs=ssp / --intr-regs=ssp" (without SIMD/eGPR regs) fallback to an RDMSR instead of XSAVE? Possibly as a future enhancement if the current patches are already upstream ready. Thanks, Ravi